The proposed research will use cell cultures to screen for toxicity of fumonisin B1(FB1) a naturally occurring mycotoxin that is both cytotoxic and carcinogenic in vivo. FB1 and related mycotoxins produced by Fusarium moniliforme occur spontaneously in corn and other grains in the USA. F. moniliforme is ubiquitous in grain crops across most of North America, and the extent of fumonisin production is not well known. FB1 is toxic to food animals and laboratory animals and hepatocarcinogenic in rats. Plans are to evaluate cytotoxicity of FB1 in both established cell lines and primary cultures from susceptible cells of species sensitive to FB1. Methods of cell evaluation used will include morphologic description, trypan blue dye exclusion, LDH enzyme release from cells, susceptibility to extracellular calcium and calcium chelates, mitogen responsiveness, tetrazolium dye reduction and fluorescence concentration. Tetrazolium reduction is proposed as a central procedure that is likely to correlate closely with many of the other tests routinely performed on cell cultures. Other tests listed will be used for comparative toxicity screening and possible mechanisms of cell damage. In vitro methods will be compared to ongoing toxicity trials in vertebrate animals susceptible to FB1.